Answer:
Yes
Step-by-step explanation:
A letter to my grandparents would be more formal, as they are older and come from a time where letters were written more often. Also, they are family, and they expect certain standards of me.
A letter to a friend would be more based off my personality and theirs, and I would write about something they would understand from our shared times. While with grandparents it would be a little more about family oriented things.